In the development of the electrolysis technique for iron, the cell-design step is crucial to ensure that the results obtained on smaller scale experiments are scaled-up to industrial size. Design criteria, based on the theorem of equipartitioned irreversibility, are proposed for the alkaline electrowinning process. One of the specific features of the process is the treatment of a multiphase electrolyte, a genuine breakthrough for electroextraction processes. Each of the unit-operations necessary to obtain the separation of the iron and oxygen from iron oxide are depicted together with the corresponding physical limitations and available technologies. Optimal solutions to obtain uniform and steady variation of each of the involved phenomena can be readily deduced from this approach and a cell-design is proposed.